Thermostatic switch



June 13, 1933. E. BLETZ THERMOSTATIC SWITCH Filed May 31. 1930 Fig. I.

INVENTOR Edward B/ezz.

ATTORNEY Batented June 13, 1933 UNITED STATES PATENT OFFICE EDWARD BLETZ, OF LEXINGTON, OHIO, ASSIGNOR T0 WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION O15 PENNSYLVANIA THERMOSTATIG SWITCH Application filed May 31,

My invention relates to thermostats, and particularly to multiple-contact thermostatic switches.

An object of my invention is to provide a simple and novel form of plural contact and plural arm thermostatic switch.

. ing element at three different temperatures of operation.

In practicing my invention, I provide a plural-contact-arm contact device normally biased to its closed position, the arms being of diiierent degrees of resiliency, a corresponding plurality of contact membersand an adjustable bimetal strip to actuate the contact arms in predetermined sequence.

In the single sheet of the drawing,

Figure l is a View partially in side elevation and partially in section of a thermostatic switch embodying my invention,

Fig. 2 is a View similar to Fig: 1 but with the bilnetal strip in its actuated position,

Fig. 3 is a partially disassembled and fragmentary view showing, more particularly, the contact members,

Fig. 4 is a view in lateral section taken on the line IV-IV of Fig. 1, and,

Fig. 5 is a top plan view of the device with the cover removed.

Referring more particularly to Figs. 1 and 2 of the drawing, a metal base member 11 is there shown as being of bar shape and as being provided with upturned lugs 12 there being one of these lugs at each side of the bar adjacent to one end portion thereof. The other end of the bar 11 is provided with a longltudinally extending recess 13 therein (see Fig. 5) and a block 14 of suitable electrio-insulating material has interfitting engagement in the recess 13, grooves 16 being provided in the block 14, as shown in Fig. 4 of the drawing. A plurality of adjustable contact terminals 17, 18 and 19 extend later- 1930. Serial No. 458,053.

ally through the member 14 and are pro vided with external screw threads to permit of properly adjusting them in the block 14, nuts 20 being provided to lock them in adj usted positions.

A plural-arm contact bar 21 is of bar shape and at one end thereof is provided with integral laterally extending lugs 22 which are bent in a plane substantially at right angles to the plane of the bar 21 to fit over and cooperate with lugs 12 to provide a pivotal mounting for the arm 21, a pin 23 extending through the overlapping lugs 12 and 22. A coil spring 24 is provided to yieldingly bias the arm 21 so that the movable end thereof will be yieldingly pressed toward the contact terminals 17, 18 and 19.

One contact member 26 is mounted directly on the arm 21 closely adjacent to the free end thereof and contact members 27 and 28 are mounted on two arms 29 and 31 which are integral with each other and are made of relative thinner strip metal, one end of which is riveted to the bar 21 by a plurality of rivets 32. The arm 21 and the arms 29 and 31 thus constitute contact, arms of dilierent degrees of resiliency.

A bimetal strip 33 has one end thereof riveted to a metal supporting strip 34, of substantially Z-shape, the other end of which is secured against base 11 by a plurality of rivets 36. The free end of the bar 33 may be bent to rounded shape so as to provide a point or line contact between the bar 33 and the contact arm 21.

include a machine screw 38 extending through the base 11, and a lock nut 39 to lock the screw 38 in any adjusted position. This permits of varying the temperatures at which disengagement and engagement of the re spective contact members occurs.

The coiled spring 24 has one end thereof resting againstthe intermediate. portion of member 34, while the other end or end portions thereof engage one or both of the lugs 22' of the arm 21.

A cover or casing 41 is provided and openings 42 may be provided therein in order to insure that the temperature of the bimetal bar will follow very closely that of the ambient air.

I have illustrated a heating element 43 which is to be controlled as to its temperature by the thermostatic switch hereinbefore described. I have found it possible to adjust the relative positions of contact terminals 17, 18 and 19 to obtain disengagement of contact member 26 from terminal 17 at one temperature, the disengagement of contact member 27 from terminal 18 at a diflerent higher temperature and the disengagement of contact member 28 from terminal 19 at a different and still higher temperature. In order to make use of this operation, I provide a manually operable switch 44 which may be of any suitable or desired kind and the movable arm of which may be selectively caused to engage contact members 46, 47 or 48, these contact members being connected by suitable conductors to terminals 17, 18 and 19.

Assuming that the contact members and the bimetal bar have been properly adjusted, if the arm of switch it engages member &6, the mean temperature of heating element 43 will be maintained at a predetermined value which, in the case of a warming pad, may be on the order of 120 F. If the arm of switch 44 engages contact member 47, the mean or average temperature of the warming pad may be on the order of 130, while if contact member 47 is engaged the average temperature may be on the order of 170. IVhile I have referred to different average temperatures, it is, of course, to be understood that these are illustrative only and that the operating temperatures may be varied within considerable limits by proper adjustments in the thermostatic switch.

The device embodying my invention may be made relatively small and is particularly applicable to warming pads in which it is very desirable that a plurality of different operating temperatures be obtainable, and I have found that a device of the kind disclosed in the present application is relatively inexpensive, easy to manufacture and locate in proper operative position in a warming pad and also that it will follow very closely the operating temperatures of the warming pad and that it will operate with little or no chattering or vibration of the cooperating contact members.

Various modifications may be made in the device embodying my invention without departing from the spirit and scope thereof, and I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art or are set forth in the appended claims.

I claim as my invention:

1. In a thermostatic switch. a base strip, a metal member, of extended Z-shape, having one of its ends secured to the base strip, a bimetal bar having one of its ends secured to the other end of the member of extended 2- shape, a contact bar pivotally mounted on said base strip spring biased toward said base strip and operatively engaged by the free end of the bimetal bar, a double arm contact spring member mounted on the contact bar and 00- operating therewith to provide a plurality of contact arms of different degrees of resiliency, and a corresponding plurality of substantially fixed contact members insulatedly mounted on and supported by the base strip.

2. In a thermostatic switch, a base strip, a metal member, of extended Z-shape, having one of its ends secured to the base strip, a bimetal bar having one of its ends secured to the other end of the member of extended Z-shape, a contact bar pivotally mounted on said base strip spring biased toward said base strip and operatively engaged by the free end of the bimetal bar, a plural arm contact spring member of greater resiliency than the contact bar mounted thereon, a plurality of contact members supported on the base strip and cooperating with the contact bar and the plural arm contact spring member.

3. In a thermostatic switch, a base strip, a metal member, of extended Z-shape, having one of its ends secured to the base strip, a bimetal bar having one of its ends secured to the other end of the member of extended Z-shape, a contact bar pivotally mounted on said base strip spring biased toward said base strip and operatively engaged by the free end of the bimetal bar, a double arm contact spring member mounted on the contact bar and cooperating therewith to provide a plurality of contact arms of different degrees of resiliency, and a corresponding plurality of substantially fixed contact members insulatedly mounted on and supported by the base strip, and an adjusting screw for moving the supported end of the bimetal bar laterally of the base strip.

4:. A thermostatic switch including a base, a bimetal bar, a member adjustably supporting the bimetal bar on the base, a plurality of contact members mounted on the base, and a contact bar pivotally supported 011 the base and having a plurality of contact arms of different degrees of resiliency thereon cooperating with the contact members on the base and actuated by the bimetal bar to disengage the cooperating contacts in sequence.

5. A thermostatic switch including a base, a bimetal bar, a strip member supporting the bimetal bar on the base, adjusting means engaging the base and the strip member to move the bimetal bar laterally of itself and the base, a plurality of contact members on the base, and a contact bar pivotally supported on the base and having a plurality of contact arms of dill'erent degrees of resiliency thereon and extending longitudinally thereof and cooperating with the contact members on the base and actuated by the bimetal bar to disengage the cooperating contacts in predetermined sequence.

6. A thermostatic switch including a base of bar-shape having a recess therein at one end, a block of electric-insulating material interfitting with the base in the recess, a pluv rality of contact members supported by said block of electricdnsulating material, a bimetal bar supported by the base, and a plural-contact bar pivotally supported by the base and having a corresponding plurality of cooperating contact members actuated by the bimetal bar to disengage the cooperating contact members in predetermined sequence.

7. A thermostatic switch including a, base having a recess at one end thereof, a birifetal bar supported on the base, a plural-contact arm pivotally mounted on the base and actuated by the bimetal bar, ablock of electric-- insulating material in the recess, and a plurality of contact terminals supported by the block and cooperating with the contacts on the arm, said block having interfitting engagement with the base, the blockand contact terminals being removable as a unit from the base.

8. A device as set forth in claim 5 in which the arms are partly coextensive.

9. A device as set forth in claim 5 in which the contact arms of different degrees of resiliency have a portion integral with each other and the device includes means for securing the integral portion to the contact bar.

In testimony whereof, I have hereunto subscribed my name this 19th day of May, 1930.

' EDWARD BLETZ; 

